Chlorofluorophosphite and Methyl Difluorophosphite

Submitted by Donald Ray Martin and Philip J. Pizzolato Checked by Paul W. TBorrt 

The method used in the preparation of methyl chloro-fluorophosphite and the corresponding difluoro ester is 

Methyl difluorophosphite is very readily obtained by the action of antimony(III) fluoride on the dichloro ester. The intermediate, partially fluorinated chlorofluoro ester is produced in appreciable yields only under carefully controlled conditions. Although the conditions outlined below, i.e., low temperature, low pressure, and slow rate of addition of fluorinating agent, favor the formation of the chlorofluoro ester, a mixture results, and the yield of the chlorofluoro ester is low compared to that of the difluoro.1 

The volatile products of the reaction are collected in the still pot P, which is surrounded by liquid nitrogen. The 

The mixture of reaction products is fractionally distilled in a modified Dufton column as described in synthesis 45. The yields based on methyl dichlorophosphite are chloro-fluorophosphite, about 8%, and difluorophosphite, about 40%. 

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III) fluoride below 10° and under a pressure of 50 mm. to produce methyl chlorofluorophosphite and methyl difluorophosphite. 

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